The Trail



 Trailside Nature & Science Center

The self-guided hike begins on the lower level of the Nature Center, to provide you with an overview of what you will see on the trail, and a graphic history of the area. Please take time to view the exhibits of basalt minerals and fluorescent minerals (in the Discovery Room) as well. When you leave the Visitor Center, turn right and walk to the highest edge of the parking lot to the marked outcrop.



 Basalt Outcrop

In the parking lot, you are standing on the ridge of the First Watchung Mountain, formed by the first, and oldest, lava flow 210 million years ago. Look down the hill, behind the trees, toward the west to see the second ridge. The low area in between the ridges formed as the softer sandstones and shales eroded more rapidly. The marked outcrop is basalt, which formed the step-like structure as the lava cooled. Basalt is also called trap rock, from the Scandinavian word “treppe” which means stair. The chemical weathering and oxidation of the iron-rich basalt produces its rusty color. Many trap rock quarries are located in the Watchung Mountains. The rock is blasted from the quarry walls and crushed to produce gravel for road stone and asphalt. Cross the parking lot and continue to the street entrance. Turn right and walk downhill on the paved road, as far as the lower edge of the parking lot.



 Erosion at Parking Lot

When rain falls on vegetated areas, most of it is absorbed by the plants and soil. When it falls on an impermeable surface such as this paved parking area, it cannot be absorbed and flows over the surface. The cumulative effect of this surface runoff can be seen at the low corner of the parking area, where the soil washed away and created a gully, which is now filled with gray gravel. Extensive paving in New Jersey — for parking lots, malls, and business parks — has led to increased runoff, erosion and flooding. The orange basalt fragments you see are highly oxidized due to abundant moisture, giving the fragments, and the soil derived from them, a typically “rusty” color. The gray gravel, recently emplaced, has not yet oxidized. Continue down the paved road to the Orange Trail entrance.



 Carriage Road

Follow the Orange Trail past the steps made of logs and rocks installed by volunteers to slow erosion of the trail. The trail was once an old carriage roadway, which led to a mill town called Feltville, now the Deserted Village. As you proceed down the trail, you will notice the banks on each side are steep. Each time a hiker walks down the trail, a little soil is loosened. When it rains, the loosened soil is washed down hill. At one time, the narrow valley you are walking did not exist. Much of the soil and rock has been transported by erosion, washed away by rainwater flowing down the slope. Continue down trail.



 Puddingstone Boulder

This huge purple boulder with white pebbles is an example of a glacial erratic. It was not formed in the Watchung Mountains, but carried by a glacier and dropped here less than one million years ago. It is a conglomerate of white quartz pebbles and purple quartzite in a purple hematite-stained matrix. The rock originated in the Green Pond area of Morris and Sussex counties, over 25 miles to the northwest. It is known as Green Pond Conglomerate or “puddingstone”. Continue down the slope until you are standing on a bumpy gray rock surface in the middle of the trail.



 Surface of Lava Flow

You are standing on the top of one of the lava flows that make up the First Watchung Mountain. This is the top surface of a series of basalt columns formed when the lava contracted as it cooled and hardened. Continue down the hill.



 Glacial Erratic

These boulders are glacial erratics, too. The term “glacial erratic” refers to any rock that was frozen into glacial ice and carried with it on its southward journey. Continue down the slope a short distance.



 Hillside Spring

This muddy spot is where the water from a hillside spring emerges at the surface and flows down the trail. There is a great supply of water stored below the surface of the Watchung Reservation. Native Americans used these springs, and today our local water company has wells that tap this water supply for our homes. Continue down the hill, which becomes the Blue Trail. Do not follow the Orange trail. Just ahead look at the stream to your left.




Streams do not flow in straight lines, but form and follow gentle curves called meanders. Water flows faster on the outside bend of the meander, eroding the stream bank there more quickly. The faster water moves, the more sediment it can carry, transporting particles of all sizes downstream. Continue on the Blue Trail. Look at the hill to the right.



 Red Sandstone & Red Shale

These are sedimentary rocks. The shale is composed of thinly-layered lithified mud that breaks easily into sheets. The sparkly surfaces are caused by bits of mica deposited with the mud. Intermixed with the shale are blockier layers of red sandstones. The shales and sandstones were deposited by streams along the edges of shallow lakes where seasonal drying occurred, and their red color is due to the chemical reaction of atmospheric oxygen with the iron in the rock. These rocks, in layers called beds, are tipped slightly to the northwest. Most of the rocks in the Newark Basin dip in this direction at an angle of about 15 degrees. This tilt is due to the movement of the Earth’s crust as the continental plates drifted apart during Jurassic time, forming the Atlantic Ocean. Continue down the hill and turn right on the bridle trail (an unmarked, wider trail). Do not stay on the Blue Trail.



 Gray Shale

(As you walk up the trail, notice many of the smaller trees with the lower portion of their trunks curved in a downhill direction. This is evidence of a form of erosion called soil “creep.” Under the influence of gravity, the soil on steep hillsides moves slowly downhill. As the trees grow, they constantly adjust their growth direction to remain upright.) At this stop, the thin papery pieces of shale are gray. This color indicates that these sediments were continuously covered with water, probably in a deeper part of a lake or swamp. The red and gray shales are part of a larger unit called the Feltville Formation. This formation is approximately 600 feet thick and overlies the basalt of the Orange Mountain Formation that forms the First Watchung Mountain. The Feltville Formation is, in turn, covered by another flow of lava known as the Preakness Basalt. This forms the Second Watchung Mountain, which rises on the other side of the swampy area.

This concludes the geology hike. You may turn around and walk back up the Orange Trail to the parking lot or you may continue up the bridle path, and bear right, which will take you to The Loop picnic area. Map of Watchung Reservation.

Interested in another informative trail? Go to the Watchung Reservation History Trail.